The biomedical research infrastructure at New Mexico Highlands University will be greatly improved by the addition of a state-of-the-art laser spectroscopic and photochemical laboratory dedicated to the study of biological molecules. The proposed laboratory will consist of a pulsed Nd:YAG laser plus OPO with wavelength accessibility ranging from 200 nm to 2000 nm plus ancillary equipment (detectors, digitizing oscilloscope, optics and mounts, and UV-visible absorption and fluorescence spectrophometers). The productivity of the research conducted at NMHU will be greatly facilitated by existing research collaborations with Prof. R.R. Birge (Chemistry, Syracuse University), Dr. G.R. Buettner (College of Medicine, University of Iowa) and Prof. P.R. Callis (Chemistry, Montana State University). The principal goal of the proposed research, which comprises the first of many sets of studies to be conducted with the proposed equipment, is to characterize the mechanism(s) responsible for the light-induced photodegradation of the model visual pigment bacteriorhodopsin (bR) which we have observed in our laboratory. Our studies to date indicate that under 254 nm irradiation tryptophan residues and/or the retinyl protonated Schiff base chromophore (RETPSB) of bR generate one or more reactive intermediates such as singlet oxygen, superoxide, hydroxyl radical, hydrogen atoms, and aqueous electrons which subsequently react with the RETPSB chromophore, leading to a complete loss of the visible absorbance of the protein. In the proposed studies we intend to (i) characterize the rates and quantum yields of bR photodegradation induced by ultraviolet and visible light, (ii) identify the reactive intermediates responsible for the photodegradation, and (iii) characterize the initial photophysical event leading to bR photodegradation via time-resolved photophysical studies of a series of bR model compounds of the form tryptophan-(CH/2)/n- RETPSB. Because of its similarities to the human visual pigment rhodopsin (RH), the proposed studies should help to elucidate the role of RH in photoinduced diseases of the human retina and may suggest strategies for preventing such diseases. Furthermore, these studies should help to elucidate the photoprotective strategies employed by halobacteria in their natural environments. Finally, these studies should provide new insights into apoprotein-chromophore interactions in visual, photosynthetic, and mitochondrial pigments.